Notes for fix:
DownloadPermission protects against unauthenticated downloads
ClassLoadingPermission - new Permission to protect against
unauthenticated Class loading.
Issues we're addressing in the DOS hole:
* Eliminate unauthenticated URL downloads.
* Eliminate unmarshalling of unauthenticated code.
* Eliminate execution of unauthenticated code.
* Eliminate StackOverflowError's in the client thread, caused by
sending spurious garbage over InputStream's.
* Eliminate StackOverflowError's in the client thread, caused by
substituted jar files or URL's from DNS cache poisoning attacks etc.
How?
* Delay granting DownloadPermission, until remote endpoint has
authenticated itself, we trust the remote endpoint to advise a
suitable URL, if it authenticates.
* Authentication by annotating a reflective proxy (additional to the
Codebase String) from the remote endpoint, used for authentication
and to provide CodeSource Certificate[]'s. This may be different
to the Service, if a remote object is marshalled elsewhere (eg
another client).
* Delay granting ClassLoadingPermission, until remote endpoint has
authenticated itself and has provided the expected CodeSource
Certificate[]'s
* Perform unmarshalling in a controlled ExecutorService thread.
So all we're doing different is authenticating the remote end and if it
authenticates permit downloading and classloading.
There is one more scenario to consider, currently this is a mechanism to
protect against download and deserialization of unknown code for smart
proxy's. But what about Service that only use reflective proxy's and
don't require downloaded code?
But what if we don't want to grant download permission or class loading
permission to a Subject we authenticate?
Currently the unmarshalling code doesn't run as the Subject after
authentication, this means the Permission grant's are only dependent on
authentication, something Michal pointed out earlier when this was proposed.
Now this code can be easily changed so the granting permission operation
is run as the Subject after authentication, this would allow us to
distinguish between different Subjects.
The drawback is that performance won't be as good, but it seems the most
logical and powerful approach.
What do you think?
There is one last obstacle, if Certificates are used to sign the jar
files, how do you effectively prevent one Subject from using another
Subject's signed CodeSource's if Code signing is used for isolation of
separate Subjects namespaces? A service could deliberately attempt to
occupy the same namespace as another Service to attempt to gain
information via shared static variables. We need to prevent this occurring.
This has to be done with the ClassLoader, but during unmarshalling, the
service proxy has not yet been verified. The authentication proxy
delivered with the MarshalInputStream may not have the same Subject as
the Service, it could be a third party.
Could it be that when the smart proxy is unmarshalled, and executed as
it's Subject, it must contain a Certificate matching the signer of the
Codebase?
We're on the cusp of solving this problem, thoughts?
Cheers,
Peter.
Peter Firmstone (JIRA) wrote:
Denial of Service during unmarshalling of smart proxy's
-------------------------------------------------------
Key: RIVER-362
URL: https://issues.apache.org/jira/browse/RIVER-362
Project: River
Issue Type: Bug
Environment: Untrusted networks
Reporter: Peter Firmstone
During unmarshalling of smart proxy's there's a period before the proxy has
been verified (authenticated) where deserialization methods are executed on
untrusted code, the potential exists for untrusted code to perform denial of
service.
